1. Field of the Invention
This invention relates to laser drivers and, in particular, to high speed laser drivers. Accordingly, it is a general object of this invention to provide new and improved laser drivers of such character.
2. General Background
A commonly used circuit for modulating diode lasers includes a differential pair of bipolar transistors which share a common emitter resistor (or, alternatively, a constant current source, such as another transistor). A separate laser biasing network was required.
The advantages of using such a laser driver of the prior art include independent control over laser modulating and biasing controls, isolation between laser and input signal, and accurate control of the modulating current shape, particularly at the low current level.
A significant disadvantage of the prior art type of driver is its speed limitations, which is caused by operating the bipolar transistors from cut-off to normal conduction.